Hypertext Transfer Protocol (HTTP) Live Streaming (HLS) is a HTTP-based media streaming communications protocol that involves breaking the media stream into a sequence of file downloads. Each file may be downloaded as one portion of a transport stream. Each downloaded file may be played in sequence to present a continuous media stream. As a given stream is played, the client may choose from multiple different alternative streams containing the same content encoded at various data rates. At the beginning of a streaming session, the client downloads a playlist file that specifies the different or alternate streams that are available.
In HLS, a given multimedia presentation is specified by a Uniform Resource Identifier (URI) to the playlist file, which itself consists of an ordered list of media URIs and informational tags. Each media URI refers to a media file that is a segment of a single continuous media stream. To play a stream, a client first obtains the playlist file and then obtains and plays each media file in the playlist in sequence.